Nickel-base alloys



Oct. 28, 1969 A. T. CAPE I NICKEL-BASE ALLOYS Filed Sept v, 1967INVENTOR.

ARTHUR T. CAPE SSHNOUVH dOONX ATTORNEYS United States Patent 3,475,165NICKEL-BASE ALLOYS Arthur T. Cape, Monterey, Calif., assiguor to CoastMetals, Inc., Little Ferry, N.J., a corporation of Delaware Filed Sept.7, 1967, Ser. No. 666,143 Int. Cl. C22c 19/02 US. Cl. 75-171 4 ClaimsABSTRACT OF THE DISCLOSURE Effect of additions of cobalt to nickel-basealloys containing chromium, tungsten, iron and boron, and particularlythe increase in Knoop hardness caused by such additions.

This invention relates generally to nickel-base alloys of the type usedfor hard surfacing.

A coating alloy known as Pratt & Whitney Aircraft Specification-PWA 693,has the following composition:

I have found, as the result of extensive tests that the Knoop hardnessesof the foregoing alloy can be greatly improved by incorporating in theaforesaid alloy cobalt, in a controlled amount such that the cobaltconstitutes from .5 to 7.5% by weight of the alloy. At the same time,the ranges of several of the other ingredients of the aforesaid alloymay be broadened without detracting from the increased Knoop hardnessesor other desirable properties of .the alloy.

This increase in Knoop hardness is illustrated in the accompanying graphwhich forms a part of this application, and in which varying amounts ofcobalt were incorporated in nickel-base alloys of slightly ditferentcompositions, as follows:

In the lower graph, the composition of the basic alloy was as follows:

Without the addition of cobalt, the average Knoop hardness, as indicatedin the graph, was 802.

With the addition to such alloy of cobalt in various amounts, theaverage Knoop hardness were as follows.

Cobalt added (percent) Knoop hardness 2.5 1092 5.0 125 8 10.0 1 168 Itis apparent from the lower graph that the maximum hardness of the alloywas established as somewhere between and 7.5% cobalt, or, more strictly,between 4 and 7.5%, and that beyond 7.5% cobalt, the hardness falls off.

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In the upper graph, the composition of the basic alloy was as follows:

Reference to this graph shows that the Knoop hardness of thes alloy,without cobalt, was 915, and that with the addition to the alloy ofcobalt in various amounts, the average Knoop hardnesses were as follows.

Cobalt added (percent) Knoop hardness 0.5 1060 0.75 1162 1.00 1192 1.51419 5.0 1450 7.5 135 1 It is apparent from the upper graph that theKnoop hardness increased very rapidly, even with as little as 0.5%cobalt, and on up to 1.5% cobalt with a maximum hardness established atsomewhere between 1.5 and 7% cobalt, and the hardness decreasingslightly beyond about 5% cobalt.

It further appears from a comparison of the two graphs that since therespective compositions were of substantially similar analysis from theviewpoint of those ingredients which do not enhance the hardness, thatthe difference in rate of hardness increase was due primarily to thedilference in the boron content of the alloys.

Stated in another way, the variation in hardness in such alloys, due tocobalt additions thereto, is apparently related, in some way to theboron content of the alloy. This relationship has not, as yet, beenfully determined, but it is clear that the addition of cobalt to suchalloys, in amounts of from 0.5 to 7.5%, does cause a marked increase inthe Knoop hardnes.

The alloys, in accordance with the invention, are encompassed within thefollowing ranges:

Broad Range Preferred Range Preferred Analysis Carbon 005-1. 00 0. l-O.7 0. 5 Silicon 2. 5-4. 2. 54. 00 3. 75 Chromium 6-16 10-13 12 Tungsten717 15-17 16 Iron 2-5 2. 5-4. 3 3. 75 Boron 1. 00-5. 00 1. 75-3. 25 3.00 Cobalt 0. 5-7. 5 2-5 2-2. 5 Nickel Remainder Remainder RemainderHaving thus described my invention, 1 claim:

1. A nickel-base alloy consisting of from 0.005 to 1.0% carbon, 2.5 to4.75% silicon, 6 to 16% chromium, 7 to 17% tungsten, 2 to 5% iron, 1 to5% boron, 0.5 to 7.5% cobalt, and the remainder essentially all nickel.

2. A nickel-base alloy consisting of from 0.005 to 1.0% carbon, 2.5 to4.00% silicon, 10 to 13% chromium, 15 to 17% tungsten, 2.5 to 4.3% iron,1.75 to 3.25% boron, 2 to 5% cobalt, and the remainder essentially allnickel.

3. A nickel-base alloy consisting of about 0.5% carbon, about 3.75%silicon, about 12% chromium, about 16% 3 4 tungsten, about 3.75% iron,about 3% boron, 2 to 2.5% References Cited cobalt, and the remainderessentially all nickel.

4. The method of increasing the Knoop hardness of UNITED STATES PATENTSnickelbase alloys consisting of from 0.005 to 1.00% car- 2,481,976 9/1949 Cape 75-171 bon, 2.5 to 4.75% silicon, 6 to 16% chromium, 7 to 17%5 2 53 39 1 1959 Gonser 75 7 tungsten, 2 to 5% iron, 1 to 5% boron, andbalance nickel, 2 875 043 N19 75 171 which consists in adding to saidalloys cobalt in amounts of from 05 to RICHARD 0. DEAN, Primary Examiner

